I do not play with one, but I do play with a Razer Nostromo and Naga. Therefore I could totally be wrong here, but I know I can change the way my buttons look on screen. Basically I can see a 12 buttons in one row (well 36 buttons, in 3 rows going Right to left on my screen), I can change them to a Game Controller look (the crossbar). Now I would assume the Sabertooth uses Synapse 2.0 to config? In game, open the UI control panel and select to see more Action bars, sign these buttons to w/e modifier you want (like Back Trigger + Another button). If pushing these buttons doesn't work already in-game, then in Synapse 2.0 you would need to set up the Trigger (re-sign) as a Modifier (Like CTRL, SHIFT, ALT). This is how I would expect you to get more button combos going.

Ok maybe select was wrong, in one of the menus there is a select button that will make the action bars show up. When you open the UI (HUD Layout) you will see everything that can be moved. Default UI only shows Action Bar 1 & 2 (1 through =, and CTRL + 1 through =). By clicking on one of the bars, the # should go from grey to white (highlight). If you exit out of the UI, that Action bar will now be seen.

I don't have a controller to test it, but I did log in to see what it looks like from normal (pc) action buttons vs game controller. I'm not seeing where it is/will show more buttons around the crossbars. Heck it didn't even show Action bar 3, or my 8.

If more buttons is what you need, and you are already playing with KB&Mouse, maybe look into a Razer Naga mouse? It will give you 17 buttons: 12 thumb buttons, 2 side buttons, scroll wheel (3 buttons: scroll up, down, and click). Without a controller to test, not sure if you would actually get more buttons out of it or not.

I was looking at the Sabertooth but I read somewhere that you can only remap to existing buttons, not add buttons. I am kinda drunk so no guarantee on that info.

This is correct. Razer products doesn't magically add more buttons into a game. More or less just remap the keyboard to your liking to use via product.

Take my Razer Naga here for example. There is a little switch button on the bottom that changes the 12 thumb buttons from the #s above the letters on a keyboard to the #s on the Num-Pad.

The Sabertooth would be the same way. It would set up and be used like a controller, but I would assume some of them back triggers I see in pics could be re-mapped buttons (well all the buttons could be re-mapped to one's liking), mainly to a modifier key giving you the ability to use like CTRL+1 for a spell/ability.